1. Field of Invention
The present invention relates to a semiconductor manufacturing process, and more particularly to a process for changing a property of an exposed photoresist layer by a track so as to compensate the subsequent processing effect.
2. Description of Related Art
Due to the rapid development of integrated circuits, minimizing the device dimension and increasing the integration level have become the mainstream in the semiconductor industry. Generally, a semiconductor device is fabricated by performing a series of processes including deposition processes, photolithography processes, etching processes, and ion implantation processes. The key technology to decide the critical dimension (CD) is in photolithography and etching.
A typical photolithography process is conducted with a photolithography tool including a track and a stepper (or a scanner). The photolithography process normally includes coating a photoresist layer on a material layer to be patterned with a coater unit of the track, partially exposing the photoresist layer by the stepper, post-exposure baking (PEB) the exposed photoresist layer with a PEB unit of the track, and developing the exposed photoresist layer with a developer unit of the track. Thereafter, an etching process is preformed to the material layer by using the developed photoresist layer as a mask, so as to transfer the patterns from the developed photoresist layer to the material layer.
Due to the non-uniform etching gas distribution, etching rates between wafer edge and center are different, resulting in different CD performance. One known method is to expose the wafer edge chips with different exposure energy, so as to compensate the difference of the post-etch critical dimensions between the edge and the center area of the wafer in advance. However, the compensation by the exposure tool cannot eliminate the variation of the critical dimension within one chip and may cause the undesired shot-related issue. Therefore, the yield and the performance of the semiconductor device are affected.